LIVE: The Dead at the Forum and KIIS-FM's Wango Tango at Verizon Wireless Amphitheater in Irvine

It's a day of tie dye and top 40 as the faithful descend upon the two L.A.-area arenas.

Jerry Garcia might have died 15 years ago, but ambling through the parking lot of the Forum on Saturday night, you'd have been hard pressed to know he's gone. Two hours before the Dead's first L.A. show in more than a half a decade, the sun-scorched asphalt was already swarming with people. The scene was a cross between a Renaissance Faire, a Bedouin crossing and the world's most pot-addled family reunion.

Limousines ferrying baby boomers idled next to Winnebagos still following a band that first formed nearly 45 summers ago. Rusting school buses cloaked in rainbow Day-Glo paint were packed to the gills with AARP-aged hippies -- the strains of "Scarlet Begonias" mingling with the smoke from dirty windows.

Not so far away, at the Verizon Wireless Amphitheater in Irvine, a very different kind of arena show was underway: KIIS-FM's Wango Tango, a top-40 blowout featuring Lady GaGa, Kelly Clarkson and the Black Eyed Peas, in addition to a host of other radio-friendly favorites, attended by hordes of screaming teenage girls.

The weekend concerts illustrated two opposing approaches to being a devoted music fan in today's pop culture landscape: Either embrace every genre and artist with the same open-minded ardor or single-mindedly invest all your energies into the one performer, group or style that defines you.

As rapper Flo Rida built up steam before performing his hit "Low" at Wango Tango, he called a couple of ladies onstage to dance with him. He looked a touch chagrined, though, when it became clear he'd be performing "Low," an ode to losing one's paycheck to strippers, with two volunteers who couldn't have been more than 14.

He shouldn't have been surprised. Wango Tango is an annual synopsis of what a wide swath of young girls have always wanted from pop music -- good cheekbones and instant gratification. Round-table shows such as Wango Tango are about sharing a pop culture currency, reveling among strangers in your mutual familiarity with something awesome. Or sometimes just something familiar.

The main point of agreement was the New York disco vamp Lady GaGa, who owned the night with her Warhol-aping set design, a solo piano interlude and costumes imaging "Blade Runner" as a gay fantasia. "Her music's so sexual, she's just hot in that leotard," said 18-year-old Jessica Siao of Orange County. "Pants are unnecessary for her."

Pants were necessary for most of the other far-flung acts, however, including hook king Soulja Boy Tell'em, charming pop-rocker Clarkson and techno-funk quartet Black Eyed Peas. All artists necessarily sported big recent hits on KIIS, and there was a palpable pleasure in the ecstatic groupthink of the crowd's responses to them, even for singles they might individually hate.

" 'Kiss Me Thru the Phone' is ridiculous, it's so annoying," said 17-year-old Brittnei Miller of Orange County. What if a boy ever signed off an amorous phone call with a line like that? "I'd want to strangle them."

An amusing side note to the concert was the constant stream of B-list actresses. Interspersed throughout the amphitheater were lesser "Hills" castmates such as Lo Bosworth, "Gossip Girl's" Leighton Meester and most of the lineup of "The Secret Life of the American Teenager." Between the sets of turgid rap-rocker Kevin Rudolf and goofy pop-punkers All-American Rejects, the spotlight and cameras swung to one aisle, where the KIIS host and a vaguely familiar young woman gave shout-outs to their favorite acts.

"Who are you?" shouted a gang of girls a few rows away.

A teenage girl with sequined eye makeup turned and grinned. "That's Khloe," she said. Confused silence. "Khloe Kardashian," she added, to "ahhs" of scornful recognition from the group.

Kardashian likely wouldn't have been recognized outside the Forum. The younger people on hand, most of whom were sharing their Dead experience with their music-loving parents, didn't seem to be too interested in starlets.

"The music is just inspirational, you hear it and you just want to start playing," said Brennan Rubin, a 10-year-old burgeoning guitarist from San Diego. Clad in a Dead shirt, alongside his father, Rob -- who attended hundreds of Grateful Dead shows during the band's heyday -- the younger Rubin admitted that most of his friends listen to pop music, but he prefers "bands that rock," from the Grateful Dead through Led Zeppelin.

Godfather in tow, Alex Verdean of Los Angeles simultaneously celebrated his 15th birthday and his first Dead show. When asked what it was about the Dead that he liked, Verdean quickly responded, "What isn't it about them?"

Most of Verdean's friends listen to psychedelic rock, but some were into the more KIIS-friendly tunes on offer at Wango Tango. While he didn't begrudge them their opinion, Verdean confessed his belief that they had "no taste in music."